Up-conversion materials are utilized in a number of different technologies. Generally described, an up-conversion material converts electromagnetic radiation at a first frequency to electromagnetic radiation having one or more higher frequencies. Up-conversion materials may be employed in displays, image-capture devices, infrared detectors, and optical communication systems.
The use of up-conversion materials capable of converting infrared electromagnetic radiation generated by inexpensive, infrared laser diodes is considered a promising approach for replacing bulky, cathode-ray-tube (“CRT”) displays and other displays, such as flat-panel displays and liquid-crystal displays (“LCDs”). For example, a display may include a transparent display screen having an array of up-conversion materials coating the screen. Each of the up-conversion materials is operable to emit visible electromagnetic radiation responsive to irradiation by infrared electromagnetic radiation from an infrared laser diode. A collimated, infrared beam is scanned to selectively irradiate and address the individual up-conversion materials. The up-conversion materials emit visible electromagnetic radiation responsive to being addressed by the infrared beam to form an image.
Different approaches for color displays and projection TVs are being considered in which multiple up-conversion materials define individual RGB triads. Each up-conversion material of an RGB triad emits red-, green-, or blue-colored light responsive to infrared electromagnetic radiation. In such an approach, a color image can be generated by controlling the intensity of the red-, green-, and blue-colored light emitted from the up-conversion materials of the RGB triads.
Although the use of an infrared excitation source in combination with up-conversion materials is considered a promising technology, efficiency of conventional up-conversion materials can still be undesirably inefficient. Many conventional up-conversion materials, such as lithium niobate, only up-convert about 1.5 percent of the infrared excitation radiation to visible light.
Accordingly, designers and manufacturers of up-conversion materials, apparatuses, and displays continue to seek more efficient up-conversion techniques capable of converting non-visible electromagnetic radiation to higher frequency electromagnetic radiation for use in displays, projection TVs, and a multitude of other applications, such as subwavelength lithography.